1. Field of the Invention
The present invention generally relates to a pair of bent dipole antennas fed with a single coaxial cable used to provide horizontally polarized, omni-directional coverage with a minimum amount of vertical cross-polarization for wireless communications.
2. Background Description
Antennas providing omni-directional coverage with a desired overhead “null’ are typically vertical polarized “whip” antennas. Whip antennas are suitable for ground based fixed structures such as antenna towers. The mobile environment has necessitated the development of smaller more integrated antenna. Printed circuit board dipole antennas have been developed to meet this need. However, these newer, smaller antennas still commonly employ vertical polarization. As the frequency spectrum becomes more crowded, these vertically polarized systems increasingly suffer from noise susceptibility, due in part to man-made noise that is in the vertical direction. Likewise, multiple communications systems within the vertical polarized environment can cause significant interference. Communications systems are beginning to use horizontally polarized antennas to hide from the vertically polarized interference of other systems. However, maximum signal strength can only be achieved if all the antennas within the system have the same polarization.
One solution to meet this need is to use a pair of horizontally positioned bent dipoles to achieve omni-directional coverage with the overhead null. This can have nulls/peaks in the pattern greater than 3 dB. Additionally, other attempts to solve this problem have used antenna array circuits fed with complicated feed networks that may not be mechanically feasible in a mobile application or are difficult to manufacture. In addition, these solutions have relied on location of transmission line and related feed points with respect to the dipole in order to tune the antenna that is difficult to maintain during production.